Irrigation Glossary

Cablegation Method of surface irrigation that uses gated pipe to both transmit and distribute water to furrows or border strips. A plug, moving at a controlled rate through the pipe, causes irrigation to progress along the field and causes flow rates from any one gate to decrease continuously from some maximum rate to zero.

Capillary radius Aditional wetted radius in soil profile beyond surface wetted radius for point source emitters.

Capillary water Water held in the capillary, or small pores of the soil, usually with soil water pressure (tension) greater than 1/3 bar. Capillary water can move in any direction.

Carryover soil moisture Moisture stored in the soil within the root zone during the winter, at times when the crop is dormant, or before the crop is planted. This moisture is available to help meet water needs of the next crop to be grown.

Catch can grid Containers spaced at regular intervals for collecting water for use in a water audit (sprinkler profile test).

Cation Positively charged ion which during electrolysis is attracted towards the cathode. Sodium, potassium, calcium and magnesium are the most common cations in waters and soil extracts.

Cation exchange capacity The sum of exchangeable cations (usually Ca, Ma, K, Na, Al, H) that the soil constituent or other material can adsorb at a specific pH, usually expressed in centimoles of charge per Kg of exchanger (cmol/Kg), or milli equivalents per 100 grams of soil at neutrality (pH = 7.0), meq/100g.

Cavitation Process where pressure in the suction line falls below the vapor pressure of the liquid, vapor is formed and moves with the liquid flow. These vapor bubbles or "cavities" collapse when they reach regions of higher pressure on their way through pumps.

Center pivot irrigation Automated irrigation system consisting of a sprinkler lateral rotating about a pivot point and supported by a number of self-propelled towers. Water is supplied at the pivot point and flows outward through the pipeline supplying the individual sprinklers or spray heads.

Centrifugal pump Pump consisting of rotating vanes (impeller) enclosed in a housing and used to impart energy to a fluid through centrifugal force.

Certified Agricultural Irrigation Specialist (CAIS) The Certified Agricultural Irrigation Specialist is involved in the management and operation of on-farm irrigation systems. These systems include surface irrigation methods, as well as pressurized systems like micro-irrigation and sprinklers. Prior to certification examination, specialists are required to take an Irrigation Association approved preparatory course.

Certified Golf Irrigation Auditor (CGIA) The Certified Golf Irrigation Auditor is involved in the analysis of turf irrigation water use tailored to the unique conditions found on golf courses. Golf Auditors collect site data, make maintenance recommendations and perform water audits on golf courses. Through their analytical work at the site, these irrigation professionals develop base schedules for greens/tees, fairways and roughs. Prior to certification examination, auditors are required to take an Irrigation Association approved preparatory course.

Certified Irrigation Contractor (CIC) The Certified Irrigation Contractor is an irrigation professional whose principle business is the execution of contracts and subcontracts to install, repair and maintain irrigation systems. The CIC must conduct business in such a manner that projects meet the specifications and requirements of the contract.

Certified Irrigation Designer (CID) The IA Certified Irrigation Designer engages in the preparation of professional irrigation designs. They evaluate site conditions and determine net irrigation requirements based on the needs of the project. The designer is then responsible for the selection of the most effective irrigation equipment and design methods. The objective of a CID is to establish specifications and design drawings for the construction of an irrigation project.

Certified Landscape Irrigation Auditor (CLIA) The Certified Landscape Irrigation Auditor is involved in the analysis of landscape irrigation water use. Auditors collect site data, make maintenance recommendations and perform water audits. Through their analytical work at the site, these irrigation professionals develop monthly irrigation base schedules. Prior to certification examination, auditors are required to take an Irrigation Association approved preparatory course.

Certified Landscape Irrigation Manager (CLIM) The Certified Landscape Manager is an irrigation professional familiar with all areas of turf irrigation design and construction management. CLIMs must be certified as CICs, CID (all Landscape/Turf specialty areas), and either as a CLIA or CGIA. Certified Landscape Irrigation Managers have extensive experience in design, construction, construction management and auditing of turf irrigation systems.

Check, Check structure Structure to control water depth in a canal, ditch or irrigated field.

Check basin irrigation Irrigation by flooding areas of level land surrounded by dikes. Used interchangeably with level border irrigation, but usually refers to smaller areas.

Check irrigation Modification of a border strip with small earth ridges or checks constructed at intervals to retain water as the water flows down the strip.

Check valve Valve used in a pipeline which allows flow in only one direction.

Chemigation Application of chemicals (including fertilizers) to crops through an irrigation system by mixing them with the irrigation water.

Christiansen's uniformity coefficient

irrigation Characteristic of the areal distribution of water in a field as the result of an irrigation.
soil Ratio of the D60 size particles passing a screen to the D10 size of a granular material.

Circuit Breaker Also called breaker. a device for interrupting an electric circuit to prevent excessive current, as that caused by a short circuit, from damaging the apparatus in the circuit or from causing a fire.

Circular mil Unit of measure used to report the cross sectional area of a wire conductor

Class (pipe) Term generally used to describe the pressure rating of SDR-PR (standard dimension ratio-pressure rated) PVC pipe. For example, a class 200 pipe has a pressure rating of 200 psi.

Class (soil) Group of soils defined as having a specific range in one or more particular properties such as acidity, degree of slope, texture, structure, land- use capability, degree of erosion, or drainage.

Clay Soil separate consisting of particles less than 0.002 mm in equivalent diameter. Naturally occurring material composed primarily of fine-grained minerals, which is generally plastic at appropriate water contents and will harden when dried or fired.

Clay Loam Loams are gritty, moist, and retain water easily. In addition to the term loam, different names are given to soils with slightly different proportions of sand, silt, and clay: sandy loam, silty loam, clay loam, sandy clay loam, silty clay loam, and loam.

Climate

Arid climate. Climate characterized by low rainfall and high evaporation potential. A region is usually considered as arid when precipitation averages less than 10 inches per year.
Humid climate. Climate characterized by high rainfall and low evaporation potential. A region generally is considered as humid when precipitation averages more than 40 inches per year.
Semiarid climate. Climate characterized as neither entirely arid nor humid, but intermediate between the two conditions. A region is usually considered as semiarid when precipitation averages between 10 and 20 inches per year.
Subhumid climate. Climate characterized by moderate rainfall and moderate to high evaporation potential. A region is usually considered subhumid when precipitation averages more than 20 inches per year, but less than 40 inches per year.

Coarse sand Coarse sand is a soil separate. Its physical size varies according to the classification system being utilized.

Coarse sandy loam Soil textural class.

Coefficient Various forms of "k" are used to describe constants, coefficients and factors.

Allowable stress factor Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the water stress.
Crop coefficient Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the plant species.
Density factor Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the density of the plant material.
Landscape coefficient Coefficient used to modify reference ET which includes species factor, density factor and microclimate factor.
Microclimate factor Factor or coefficient used to adjust reference evapotranspiration to reflect the microclimate of an area.
Pan coefficient Factor to relate actual evapotranspiration of a crop to the rate water evaporates from a free water surface in a shallow pan. The coefficient usually changes by crop growth stage.
Species factor Factor or coefficient used to adjust reference evapotranspiration to reflect plant species.

Coefficient, consumptive use Ratio of volume of irrigation water consumptively used to the total volume of irrigation water that has left the region, both in a specified period of time.

Coefficient of retardation Values describing the hydraulic frictional characteristics of a pipe material.

Coefficient of runoff Runoff coefficient used in the rational method of predicting a design peak runoff rate. It helps to characterize runoff rate from a watershed area.

Coefficient of manufacturing variation: See manufacturer's coefficient of variation.

Coefficient of uniformity

irrigation Characteristic of the areal distribution of water in a field as the result of an irrigation.
soil Ratio of the D60 size particles passing a screen to the D10 size of a granular material.

Cohesion Attraction of water molecules to each other. Attraction of like substances to one another. In soils, it is the process that forms a film of water around soil solids.

Common Wire The wire that brings power to the switch or fixture.

Compensating emitter Emitter designed to discharge water at a near constant rate over a wide range of lateral line pressures.

Compression Fitting A brass or plastic fitting used to join pipe by tightening two nuts that force a ring like ferrule into the fitting to assure a tight seal.

Consumptive use Total amount of water taken up by vegetation for transpiration or building of plant tissue, plus the unavoidable evaporation of soil moisture, snow, and intercepted precipitation associated with vegetal growth.

Continuous-flow irrigation System of irrigation water delivery where each irrigator receives the allotted quantity of water continuously.

Continuous flushing emitter Micro irrigation system emitter designed to continuously permit passage of large solid particles while operating at a trickle or drip flow, thus reducing filtration requirements.

Control structure Water regulating structure, usually for open channel flow conditions.

Controller An electric timing device that operates each (irrigation) zone for a predetermined time and frequency.

Conveyance efficiency Ratio of the water delivered, to the total water diverted or pumped into an open channel or pipeline at the upstream end.

Conveyance loss Loss of water from a channel or pipe during transport, including losses due to seepage, leakage, evaporation, and transpiration by plants growing in or near the channel.

Corporation stop (valve) Quarter turn valve similar to a ball valve with two exceptions. Internally there is a circular disk rather than a ball, and there is no attached handle. A corporation stop is located at the tap-in; it is usually made of brass and is installed using a special tool that doesn't require shutting off the water supply.

Corrugation irrigation Method of surface irrigation similar to furrow irrigation, in which small channels, called corrugations, are used to guide water across a field. No attempt is made to confine the water entirely to the corrugations.

Coupler or Coupling Device, either self-sealed or mechanically sealed, that connects the ends of two lengths of pipe or pipe to a hose.

Crop coefficient Coefficient used to modify reference evapotranspiration to reflect the water use of a particular plant or group of plants particularly with reference to the plant species.

Crop evapotranspiration Amount of water used by the crop in transpiration and building of plant tissue, and that evaporated from adjacent soil or intercepted by plant foliage. It is sometimes referred to as consumptive use. Crop evapotranspiration is the quantitative amount of ET within the cropped area of a field, and which is associated with growing of a crop.Same as plant water requirement.

Cross connection Any actual or potential connection or structural arrangement between a public or private potable water system and any other source or system through which it is possible to introduce into any part of the potable system any used water, industrial fluids, gas, or substance other than the intended potable water with which the potable system is supplied. By-pass arrangements, jumper connections, removable sections, swivel or change-over arrangements or other "temporary" arrangements through which backflow could occur are considered to be cross-connections. See also Backflow.

Crop growth stages Periods of like plant function during the growing season. Usually four or more periods are identified.

Initial- Between planting or when growth begins and approximately 10 percent ground cover.
Crop development- Between about 10 percent ground cover and 70 or 80 percent ground cover.
Mid season- From 70 or 80 percent ground cover to beginning of maturity.
Late- From beginning of maturity to harvest.

Crop water stress index Index of moisture in a plant compared to a fully watered plant, measured and calculated by a CWSI instrument. Relative humidity, solar radiation, ambient air temperature, and plant canopy temperature are measured.

Cumulative intake Depth of water absorbed by soil from the time of initial water application to the specified elapsed time.

Curb stop Valve The curb stop valve is located at the property line; it controls the flow of water to the residence. The curb stop is similar to the corporation stop but it is used to shut off the water for repairs, nonpayment of water bills, or flooded basements. Since the corporation stop is usually inaccessible, the curb stop is used as the isolation valve. The curb stop is in an access box, and a long-handled wrench or "key" is used to reach the valve.

Current Movement or flow of electrons

Cutback irrigation Reduction of the furrow or border inflow stream after water has advanced partially or completely through the field in order to reduce runoff.

Cycle time Length of water application periods, typically used with surge irrigation.